1. Field of the Invention
The present invention relates to an apparatus for measuring a surface profile, which has a contact type measuring probe.
2. Description of the Related Art
For example, there is an apparatus disclosed in JPN. PAT. APPLN. KOKAI Publication No. 7-260471, as the conventional example of an apparatus for measuring the surface profile of a object to be measured. The conventional apparatus will be described below with reference to FIG. 12.
The above conventional -apparatus comprises a measuring probe 41 an X-Z coordinate system driving section 42, a coordinate measuring section 43, an input means 44, and control means 45. More specifically, the measuring probe 41 includes a contact needle member 41a, which makes contact with an object to be measured 32 driven in a Y-axis direction by a Y-axis coordinate system driving section 31 provided in a main body 30 of the above apparatus. In this case, the needle member 41a contacts the object 32 to be measured from above. The X-Z coordinate system driving section-42 drives the measuring probe 41 in the X and Z directions, and the coordinate measuring section 43 measures the coordinates of the measuring probe 41. The input means 44 inputs tilt angle information of the contact needle member 41a at a contact measuring point with respect to a surface 32a to be measured. The control means 45 controls the measuring pressure of the measuring probe 41 on the surface of the object to be measured based on the tilt angle information inputted by the input means 44. In this case, the control means 45 controls the contact by the measuring probe 41 so that the sum of contact deformation of the measuring probe 41 and the object 32 to be measured becomes constant in the vertical direction to the surface to be measured 32a. 
The conventional apparatus has the above structure, and the tilt angle information at the contact measuring point by the measuring probe 41 on the surface of the object to be measured is input from the input means 44. Based on the tilt angle information thus input, the apparatus can measure the surface profile of the measuring surface 32a of the object 32 to be measured while controlling the measuring pressure of the measuring probe 41 by the control means 45. As described above, the measuring pressure of the measuring probe 41 is controlled, and thereby, vertical contact deformation is always made constant with respect to the surface of the object to be measured. By doing so, it is possible to prevent the generation of a measuring error resulting from changes of the contact deformation.
In the above conventional apparatus, a flat spring or a compression coil is used for controlling the measuring pressure so that the measuring pressure of the measuring probe 41 becomes extremely small, or the contact force always becomes constant on the surface of the object 32 to be measured.
According to a first aspect of the present invention, there is provided an apparatus for measuring a surface profile of an object to be measured, comprising:
a measuring probe positioned to contact the surface of the object to be measured;
guide means for supporting and guiding the measuring probe in an axial direction of the measuring probe;
tilt angle adjustment means for tilting the guide means at a predetermined tilt angle with respect to a horizontal direction so that the measuring probe contacts the surface of the object to be measured with a predetermined contact force, and
drive means for relatively driving at least one of the measuring probe and the object to scan the surface of the object to be measured with the measuring probe,
the contact force being derived from a tilt direction component of the gravity of the measuring probe generated when the measuring probe is tilted.
Preferably, the tilt angle ranges from 0.0005 to 5xc2x0, more preferably from 0.03 to 0.2xc2x0. The contact force ranges from 5 to 300 mgf, more preferably from 30 to 90 mgf.
The apparatus has the above structure, and thereby, the contact force of the measuring probe applied to the surface of the object to be measured is derived from the tilt direction component of the gravity of the measuring probe. Therefore, there is no need to take the hysteresis characteristic into consideration. A constant contact force is applied to each point on the surface of the object to be measured. Since the measuring probe is tilted at the predetermined tilt angle by the tilt angle adjustment means, an extremely small contact force can be very readily obtained. Since the extremely small contact force is obtained as described above, the apparatus is a contact type; nevertheless, it is possible to highly accurately measure the surface profile of the object to be measured. Further, it is possible to obtain effects similar to non-destructive measurement of the surface profile of the object to be measured with non-contact.
According to a second aspect of the present invention, there is provided an apparatus for measuring a surface profile of an object to be measured wherein the guide means movably supports the measuring probe, and comprises a guide mechanism to guide the measuring probe with a predetermined frictional force between the guide means and the measuring probe, the frictional force being smaller than the tilt direction component of the gravity of the measuring probe.
According to the present invention, means generating an extremely stall frictional force, for example, a linear guide, preferably, an air slider is used as the guide means. By so doing, since an extremely small contact force is obtained, the apparatus is a contact type; nevertheless, it is possible to highly accurately measure the surface profile of the object to be measured.
According to a third aspect of the present invention, there is provided an apparatus for measuring a surface profile of an object to be measured wherein the tilt angle adjustment means tilts both the measuring probe and the object to be measured at a predetermined tilt angle to the horizontal direction.
According to the present invention, since the tilt angle is applied to both the measuring probe and the object to be measured, when the object is measured, no angle difference is generated between the measuring probe and the object to be measured. Therefore, there is no need to correct the tilt angle, and the apparatus is a contact type; nevertheless, it is possible to highly accurately measure the surface profile of the object to be measured.
According to another aspect of the present invention, there is provided an apparatus for measuring a surface profile of an object to be measured wherein the object to be measured has a predetermined surface roughness Ry and scanning length xcfx86, and when a predetermined contact force Fxcex8 is applied at the maximum contact angle xcex1max by the measuring probe, the maximum velocity Vmax of the measuring probe scanning the surface of the object to be measured has a relationship expressed by the following equation:
Vmaxxe2x88x9d(Fxcex8xc2x7xcfx86)/(Ryxc2x7xcex1max)
According to the present invention, if the object to be measured is formed of a very soft material that is liable to damage when measuring, the contact force Fxcex8 is made small, and thereby, the object can be measured with the small contact forces Fxcex8 without being damaged. Conversely, if there is no possibility that the object to be measured will be damaged, the contact force Fxcex8 is made large, and thereby, the maximum scanning velocity Vmax becomes large. As a result, it is possible to shorten the time for measuring the surface profile of the object to be measured.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.